The present invention relates to the preparation of allylic compounds. More particularly, the present invention is a process for preparing allylic compounds by a transetherification reaction.
Transetherification reactions are extremely rare. Outside of certain specialized reactions, the process is not satisfactorily adapted to general use because of the difficulty in forming stable carbonium ion leaving groups from the ether starting reactants.
U.S. Pat. No. 2,847,478 (incorporated herein by reference) describes the unpressurized transetherification of diallyl ether with alcohols employing a homogeneous catalyst system comprising a salt of mercury and a strong acid cocatalyst. It is taught that the presence of the homogeneous acid alone is not sufficient to catalyze the reaction. The process is not well suited to commercial implementation due to the toxic nature of the mercury-containing catalysts.
British Pat. No. 913,919 and U.S. Pat. No. 3,250,814 (both incorporated herein by reference) describe the unpressurized preparation of allyl ethers by reacting allyl alcohols or organooxyallyl alcohols and by reacting diallyl ether with aliphatic alcohols, respectively. Both references teach the use of a catalyst system of a cuprous salt and an acid cocatalyst. Neither reference teaches that an acid alone, whether homogeneous or heterogeneous, is sufficient to catalyze the reactions. Cuprous salts, too, are by nature toxic.